<h4>Tool</h4><table border="0"><tr><td valign="top"><b>Name</b></td><td valign="top">Topographic Wetness Index (TWI)</td></tr><tr><td valign="top"><b>ID</b></td><td valign="top">20</td></tr><tr><td valign="top"><b>Author</b></td><td valign="top">O.Conrad (c) 2003</td></tr><tr><td valign="top"><b>Specification</b></td><td valign="top">grid</td></tr></table><hr><h4>Description</h4>Calculation of the slope and specific catchment area (SCA) based Topographic Wetness Index (TWI)

References:

Beven, K.J., Kirkby, M.J. (1979):
A physically-based variable contributing area model of basin hydrology'
Hydrology Science Bulletin 24(1), p.43-69

Boehner, J., Selige, T. (2006):
Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation'
In: Boehner, J., McCloy, K.R., Strobl, J.: 'SAGA - Analysis and Modelling Applications', Goettinger Geographische Abhandlungen, Vol.115, p.13-27

Moore, I.D., Grayson, R.B., Ladson, A.R. (1991):
'Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications'
Hydrological Processes, Vol.5, No.1
<hr><h4>Parameters</h4><table border="1" width="100%" valign="top" cellpadding="5" rules="all"><tr><th>Name</th><th>Type</th><th>Identifier</th><th>Description</th><th>Constraints</th></tr>
<tr><th colspan="5">Input</th></tr><tr><td>Slope </td><td>Grid (input)</td><td>SLOPE</td><td></td><td></td></tr><tr><td>Catchment Area </td><td>Grid (input)</td><td>AREA</td><td></td><td></td></tr><tr><td>Transmissivity (*)</td><td>Grid (optional input)</td><td>TRANS</td><td></td><td></td></tr><tr><th colspan="5">Output</th></tr><tr><td>Topographic Wetness Index</td><td>Grid (output)</td><td>TWI</td><td></td><td></td></tr><tr><th colspan="5">Options</th></tr><tr><td>Area Conversion</td><td>Choice</td><td>CONV</td><td></td><td>Available Choices:
[0] no conversion (areas already given as specific catchment area)
[1] 1 / cell size (pseudo specific catchment area)
Default: 0</td></tr><tr><td>Method (TWI)</td><td>Choice</td><td>METHOD</td><td></td><td>Available Choices:
[0] Standard
[1] TOPMODEL
Default: 0</td></tr></table>(*) <i>optional</i>